Safety knob



March 21, 1950 J. G. scHRAMM SAFETY KNOB Filed Aug. 23. 1948 IRA/1654M;

Jam? Schramm Patented Mar. 21, 1950 UNITED STATES PATENT OFFICE SAFETY KNOB John G. Schramm, Milwaukee, Wis. Application August 23, 1948, Serial No. 45,692

6 Claims.

This invention relates to actuating knobs for gas stoves and other appliances in which actuation of a part requires manual rotation of a shaft.

In many devices and appliances, and especially in gas ranges, it is desirable to provide some assurance against accidental actuation of the valve controls or manipulation thereof by small children.

It is, therefore, an object of this invention to provide a simple, efiicient actuating knob which embodies a safety feature whereby the control will be reasonably secure against accidental displacement and actuation by small children.

Another object of this invention is to provide an actuating knob of the character described which can be readily substituted for present actuating knobs without in anywise requiring alteration of the stems or shafts upon which they are mounted.

Another object of this invention is to provide a safety knob of the character described which is so constructed that it lends itself well to inexpensive production by plastic molding.

A still further object of this invention is to provide a knob of the character described which, when in place, coacts with the front panel of the range or other appliance with which it is used to render direct access to the shaft or stem of a valve or other control extremely difficult.

Another object of this invention is to provide a control knob having means for visually indicating the position of rotation of the part being controlled which means is nevertheless substantially entirely encased by the knob proper, with the latter being normally free to be turned without imparting rotation to the shaft or stem being controlled.

With the above and other objects in view. which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise em- 45 bodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a perspective view illustrating in broken lines a portion of a gas range and showing the application of this invention thereto;

Figure 2 is a longitudinal sectional view through the knob of this invention, said view being taken along the plane of the line 2-2 in Figure 1:

Figure 3 is a longitudinal sectional view showing the parts in their driving positions;

Figure 4 is a perspective view of the entire knob structure with the parts thereof disassembled; and

Figure 5 is a side elevational view illustrating a slight modification of the present invention, a portion being cut away to show detail.

Referring now particularly to the accompanying drawing, the numeral 5 designates a gas range having the customary burners (not shown) to which the supply of gas is controlled by valves (also not shown) adapted to be opened by the turn of a shaft or stem 6.

The shaft of each valve protrudes through the front wall l of the range and the safety actuating knob of this invention indicated generally by the numeral 8 is mounted on this protruding portion. This safety actuator comprises a hub 9 provided at its rear with an axial well It having a substantially D-shaped cross section and thus adapted to be press-fitted onto the stem or shaft 6 which has a flattened side, as at H, whereby the hub is secured against rotation with respect thereto.

The front end of the hub is reduced in diameter to provide a pilot stem l2, and a bore l3 extends axially through the hub to permit a screw it to be projected therethrough, the head of the screw being received in a counterbore l5 which communicates with the well ill. Fitted over the hub is a knob I8 having a recess H to receive the hub and a socket [8 extending from the bottom of the recess to receive the pilot stem ii. The socket [8 has a diameter substantially equal to that of the pilot stem I2, so that the knob is rotatably journaled thereon, but the socket is longer than the pilot stem ii to accommodate a compression spring Ill.

The screw l4 threads into the knob to hold the parts against separation, and enable the knob and hub to be moved axially a limited distance with respect to one another without disengagement of the pilot stem from the socket. The compression spring l9 fitted in the socket reacts axially between the knob and the hub to yieldingly hold these parts axially separated to the extent permitted by the screw.

Extending radially inwardly from the side wall of the recess are four lugs 20, and formed in the adjacent portion of the hub are four complementary notches 2!. In the normal position of the parts maintained by the spring IS the lugs 20 are held out of the notches 2|, but as will be readily apparent, upon the application of inward pressure upon the knob as shown in Figure 3 the lugs may be engaged in the notches to drivingly connect the knob with the hub. The lugs and sockets thus provide the cooperating elements of a jaw clutch normally held disengaged by the 3 spring I 8 but engageable by pressure upon the knob against the bias of the spring.

Thus, as long as the clutch is disengaged the knob is free to turn without danger of imparting rotation to the hub and consequently to the In order that the position of the shaft and the valve controlled thereby may be visually depicted the hub has an indicator finger 23 extending radially therefrom under the skirt 22, with only the small end of the finger being visible. If desired, the skirt may be made transparent as shown in Figure 5, and in this case the skirt may be provided with a downturned edge 24 to more effectively close off access to the hub.

From the foregoing description taken in connection with the accompanying drawings it will be readily apparent to those skilled in the art that this invention provides a safety knob especially adapted for use on gas stoves and other appliances, and that by virtue of its simplicity the actuator of this invention lends itself well'to inexpensive production by means of plastic molds.

What I claim as my invention is:

1. In combination with a device controlled by manual rotation of a shaft: a wall through which the shaft protrudes; a hub non-rotatably fixed to the shaft in juxtaposition to the wall; a knob recessed to receive the hub and having a skirt overlying and directed toward the wall; means freely rotatably connecting the hub and the knob, said means allowing limited axial movement of the knob with respect to the hub but at all times holding the knob in a position in which its skirt coacts with the wall to render direct access to the hub difiicult; an indicator on the hub positioned under the skirt of the knob for indicating the position of rotation of the hub and shaft; a spring reacting axially between the hub and knob for yieldingly retaining said parts in predetermined relative positions axially of one another; and cooperating clutch elements on said hub and knob normally maintained out of engagement by said spring but adapted to be brought into engagement by axial shifting of the knob against the bias of said spring so that rotation of the knob may be imparted to the hub and shaft by persons familiar with the requirements while at the same time a measure of protection is afforded against rotation of the shaft by small children.

2. The combination of claim 1 further characterized by the fact that said skirt of the knob is transparent to enable the indicator to be visible therethrough. 1

3. An actuator of the character described comprising: a hub adapted to be fixed to a shaft to be turned; a knob having a recess to receive the hub and an outwardly flared skirt covering the projected area of the hub face to preclude grasping the hub; means freely rotatably connecting the knob and hub, said means allowing limited axial movement of the knob with respect to the hub but holding said parts against axial separation beyond a position at which the recessed knob precludes grasping the hub; an indicator on the hub located under the skirt and adapted to show the position of rotation of the hub; a spring reacting axially between the hub and knob for yieldingly urging said members apart; and cooperating clutch elements on said hub and knob normally maintained out of engagement by said spring but adapted to be brought into engagement in any one of a number of relative positions of rotation by axial shifting of the knob against the bias of said spring.

4. The structure of claim 3 further characterized by the fact that said skirt is transparent to permit the indicator to be visible therethrough.

5. An actuator of the character described, comprising: a hub adapted to be nonrotatably and coaxially fixed to a rotatable control shaft projecting through a wall, said hub having its front portion reduced in diameter to provide a pilot stem; a knob having at its rear a recess to receive the hub and an axial socket extending forwardly from the bottom of said recess to freely rotatably journal the knob on the pilot stem and enable axial sliding movement of the knob with respect to the hub, said knob being of a size to cover the projected area of the hub face to thus preclude grasping the hub when the actuator is in place; a spring in the socket of the knob bearing against the pilot stem to yieldingly urge the hub and knob apart; a pin extending axially through the pilot stem of the hub and engaged with the knob to hold the knob and hub together against the force of said spring while permittingthem limited freedom of axial movement with respect to one another; and interengageable clutch elements on the hub and knob normally held out of engagement by the spring but engageable by axial rearward movement of the knob against the force of the spring.

6. In an actuator of the type adapted to impart rotation to an actuating shaft: a hub having a bore and a counterbore opening to its rear, said counterbore comprising a well adapted to non-rotatably receive a shaft; a knob having at its rear a recess adapted to receive the hub, said knob covering the projected area of the hub face to preclude grasping the hub; cooperating bearing surfaces on the knob and the hub whereby the knob is carried by the hub and is rotatable relative to the hub and axially slidable between defined limits; a pin secured in said knob with its shank projecting through the bore in the hub, said pin having an enlargedhead cooperable with the bottom of the counterbore to preclude forward axial movement of the knob beyond one of said defined limits to thus retain. said knob in place on the hub; and cooperating clutch elements on the knob and the hub adapted to be engaged by rearward axial movement of the knob to constrain the hub to rotate with the knob.

1 JOHN G. SCHRAMM.

REFERENCES CITED The following references are of record in the file of this patent:

V UNITED STATES PATENTS Number 

